The present invention relates to devices for locating and locking in position components of pressed sheet metal which are to be subjected to a welding operation. In particular, the invention relates to clamp devices of the type comprising:
a first element for supporting the sheet metal elements, which is rigidly connected to a fixed support structure, and PA1 a second element for clamping the sheet metal elements to be welded, which is supported by a body carried by said fixed supporting structure so as to be displaceable between an inoperative position, spaced from the first supporting element, and an operative position, in which it is adjacent to the first supporting element and cooperates therewith for clamping the components of sheet metal to be welded.
The clamp devices of the above indicated type have been known and used for a long time, for instance in assembling operations by means of welding of units constituted by elements of pressed sheet metal, such as motor-vehicle bodies or subassemblies thereof.
For a prompt reference, FIG. 1 shows one embodiment of a clamp device according to the prior art. Typically, with reference to this drawing, a structure 1 of pressed sheet metal is constituted by two sheet metal elements 2, 3 which must be welded by means of electric spot welding at two juxtaposed flanges 2a, 3a thereof. Elements 2, 3 are clamped in the proper welding position by means of a clamp device 4 comprising a fixed supporting element 5 and a movable clamp element 6 adapted to be closed over supporting element 5 to clamp the two juxtaposed flanges 2a, 3a in the proper welding position, so that these flanges can then be welded to each other by applying electric welding spots at areas not covered by the two elements 5, 6 of the clamp device 4. The fixed supporting element 5 is connected by screws to a fixed supporting structure 7 by means of an angled member 8. Registering plates 9, 10 are interposed between the angled member 8 and the fixed structure 7 and the supporting element 5, respectively. The movable clamp element 6 is pivotally supported around an axis 11 by a supporting body 12 which on its turn is secured by screws to the structure 7 with the interposition of a registering plate 13. A registering plate 14 is also interposed between the movable clamp element 6 and a lever 15 which is directly pivotally mounted around axis 11 on the body 12 and whose rotation is driven by a fluid cylinder 16 which is also carried by body 12. In the known device, the use of registering plates 9, 10, 13, 14 is due to the need of assuring that elements 5, 6 of the clamp device 4 are in the required proper position relative to the position of the structure to be welded 1. Typically, the structure 1 is brought to a welding station and located in position therein by means independent from the clamp device 4. Therefore, the position of the structure 1 to be welded is to be considered as predetermined and is then necessary that elements 5, 6 are at a proper position relative thereto. When the structure 1 reaches the welding station, it is arranged on the supporting element 5, in the condition shown in FIG. 1, but, obviously, with the movable clamp element 6 in an upwardly rotated condition with respect to that shown in FIG. 1. Once the structure 1 has been positioned on the supporting element 5, the cylinder 16 may then be activated to drive a closing movement of the movable clamp element 6 over the two juxtaposed flanges 2a, 3a of the two components of sheet metal 2, 3, as to obtain precise location and clamping of these flanges between the two elements 5, 6.
As it is clearly apparent, in the known solution, if it is necessary to register the position of the supporting element 5, the plates 9, 10 must be replaced with plates having different thickness, so as to adjust the position of element 5 along the two orthogonal axes (vertically and horizontally) lying in the plane of FIG. 1. Similarly, a registration of element 6 along the horizontal and vertical direction implies replacement of plates 13, 14.
Therefore, the adjustment operations on clamp devices according to the prior art are troublesome and time consuming and imply a loss in the projectivity of the plant where these devices are used.